Configure Internal Networking in Oracle VirtualBox

Learn how to connect VirtualBox guest VMs through an isolated Internal Network, configure shared network names, assign IP addresses, and test connectivity.

Internal Network is a VirtualBox network attachment mode for connecting guest virtual machines (VMs) to an isolated virtual network inside the host. Traffic stays within the host's virtual networking environment and is visible only to guest machines attached to the same internal network.

This guide explains how to configure an existing VM in Oracle VM VirtualBox Manager, connect multiple guests, configure guest-side IP addressing, and troubleshoot common connectivity problems.

What Internal Networking Does

A Guest VM is a virtual machine running under VirtualBox. A network adapter is the virtual network interface assigned to that VM. When an adapter is set to Internal Network, VirtualBox places it on a private virtual network that can connect to other appropriately configured guest adapters.

Internal networking provides guest-to-guest communication without connecting those guests to the host's physical network, the host operating system, or the internet. The host provides the virtualization environment, but it is not automatically a participant in the internal network.

Traffic remains inside the host's virtual environment.
Only guest VMs attached to the same internal network can use that segment.
The configuration is isolated from the host's physical network and external networks.
The host does not need an active external network connection for the guests to communicate.

When to Use an Internal Network

Choose Internal Network when a lab requires isolated VM-to-VM communication. It is useful for a server-client exercise, a private multi-VM test topology, or security testing that must remain contained within the virtual environment.

For example, a client VM and a server VM can communicate over an internal network while the host's Wi-Fi or wired connection is disconnected. The guests still need compatible IP addresses, but they do not need internet access or a connection to the physical LAN.

Internal Networking Compared with Bridged Networking

Bridged networking connects a guest through one of the host's physical network interfaces. The guest can appear on the same physical network as the host, subject to the network's addressing and access controls. Internal networking instead creates a guest-only segment and does not depend on a physical network interface.

Characteristic	Internal Network	Bridged Networking
Traffic visibility	Visible to guests attached to the same named internal network.	Uses the physical network and may be visible to other devices on that network.
Connection to physical host network	No connection to the host's physical network.	Uses a host physical network interface.
Guest-to-guest communication	Guests on the same internal-network name can communicate when IP settings permit it.	Guests can communicate through the bridged physical network when the network permits it.
Operation when host has no network connection	Guest-to-guest communication can continue because no physical connection is required.	Connectivity can be affected because the mode depends on the host's physical interface and network.
Typical use case	Isolated labs, private test topologies, and contained security testing.	Testing services that must be reachable from the physical LAN.

Use Configure Bridged Networks when a guest must connect to a physical network. For an overview of attachment modes, see VirtualBox Network Modes.

Configure an Existing VM in VirtualBox Manager

Use VirtualBox Manager to configure the virtual adapter before starting the VM, or shut down a running VM before changing settings that require the VM to be powered off.

Select the existing virtual machine in Oracle VM VirtualBox Manager.
Open the VM's Settings dialog.
Select Network.
Choose the adapter to configure, such as Adapter 1.
Select Enable Network Adapter.
Set Attached to to Internal Network.
Enter or select an Internal network name. This name identifies the virtual segment to which the adapter belongs.
Select OK to save the changes.

Setting	Required Value	Purpose
Network Adapter	The adapter you want to use, such as Adapter 1	Selects the virtual interface being configured.
Enable Network Adapter	Selected	Allows the guest operating system to use the virtual interface.
Attached to	Internal Network	Places the adapter on an isolated guest-only segment.
Internal Network Name	A shared name, such as `isolated-lab`	Determines which guest adapters share the same virtual segment.
Save changes	Select OK	Applies the adapter configuration.

Connect Multiple Guest VMs

Every guest that should communicate must have an enabled adapter attached to Internal Network. The adapters must use the same internal network name. The name is the shared identifier for the segment; it is not an IP address.

For example, attach both a client VM and a server VM to the internal network named isolated-lab. If a third VM uses the name management-lab, it is on a different isolated segment and cannot directly communicate with the first two through those adapters.

Two-VM Isolated Lab

Open the client VM's Network settings and enable an adapter.
Set the adapter's attachment type to Internal Network.
Set the internal network name to isolated-lab.
Repeat the same configuration for the server VM.
Configure compatible IP addresses in both guest operating systems, or provide DHCP from a service running on the internal network.
Start both VMs and test reachability from the client to the server.

The expected result is communication between the two guests without requiring the host to be connected to an external network.

Separate Isolated Networks

Place two lab VMs on isolated-lab and another VM on test-lab. The first two VMs can communicate if their guest addressing and firewalls permit it. The VM on test-lab remains isolated from them through these adapters.

Configure Guest-Side IP Addressing

Attaching an adapter to an internal network does not assign a usable IP address. The guest operating system must receive an address from DHCP or be configured with a static address.

For a simple two-VM lab, use addresses in the same subnet, for example:

Server VM: 192.168.50.10/24
Client VM: 192.168.50.20/24
Default gateway: not required for guest-to-guest traffic

The /24 prefix represents the subnet mask 255.255.255.0. Both addresses are in the same subnet, so the guests can attempt direct communication. The exact commands for applying these settings depend on the guest operating system.

Alternatively, run a DHCP service on one guest connected to the internal network. The DHCP service must be reachable on that isolated segment and must provide addresses appropriate for the lab subnet.

After the VMs are running, use a basic connectivity test from one guest to the other, such as pinging the other guest's IP address. If the test protocol is blocked, check the guest firewall and use an appropriate rule or another permitted test.

Connectivity Validation Checklist

Confirm that every participating VM has its adapter enabled.
Confirm that every participating adapter is attached to Internal Network.
Compare the internal network name on each adapter.
Check that each guest recognizes its virtual network adapter.
Check that the guests have compatible IP addresses and subnet masks.
Verify that a DHCP service exists if the guests are configured for automatic addressing.
Check guest firewall rules for the protocol used by the connectivity test.
Run a guest-to-guest connectivity test after both VMs are running.

Troubleshooting

Two Guest VMs Cannot Communicate

Disabled adapter: Confirm that Enable Network Adapter is selected for both VMs.
Different internal network names: Compare the names exactly. Adapters on different names are on different isolated segments.
Incompatible addressing: Check each guest's IP address and subnet mask. The addresses must be appropriate for communication on the same subnet, unless routing has been deliberately configured.
Guest firewall: Check whether the firewall blocks ping or the application protocol being tested.

A Guest Cannot Reach the Internet or Host Network

This is expected when the only configured adapter uses Internal Network. That mode is designed for isolated guest-only communication.

If the lab requires both isolation and external access, consider adding another virtual adapter with a suitable attachment mode instead of replacing the isolated lab adapter. Review Configure Host-Only Networks when host-to-guest access is part of the design.

VMs Are Running but Have No Usable Network Connectivity

No DHCP service is available on the internal network.
Static IP settings are missing or incorrect.
The guest operating system does not recognize its virtual adapter.

Configure compatible static addresses on the guests, or provide DHCP within the internal network. Then confirm that each guest sees the adapter and has received or applied its expected IP configuration.

Exam-Relevant Notes

Internal Network isolates guest traffic from the host's physical and external networks.
Guests must use the same internal network name to share the same virtual segment.
Internal networking alone does not provide IP addresses or DHCP.
Guest operating systems still require compatible IP configuration for communication.
Bridged networking uses a host physical network interface; Internal Network does not.

Next Steps

For broader background, review Virtual Networking. If you need a network that permits communication between guests and the host, study Configure Host-Only Networks. To provide controlled external connectivity for multiple guests, see Configure NAT Networks.